At an age when my classmates were fascinated with dinosaurs or playing Cowboys and Indians, I picked up a book titled “Engineers’ Dreams” and was hooked. Thus began a lifelong interest in projects associated with engineering concepts about improving our world.
The author, Willy Ley, sketched the outlines of some large civil projects including the development of the Channel Tunnel connecting Britain with France. Of course, the tunnel has been in use for 28 years. He also explored ideas for generating electricity. With solar and wind power leading the way, every one of his generation schemes has seen significant development since.
Given my interests, I was drawn to a recent letter in The Desert Sun proposing to solve the shortage of water in the Southwest by bringing water from the Mississippi River.
This is not the first proposal to find water for the Southwest. One such scheme, made more than 50 years ago, would have brought water from Alaska and Canada to feed into the Columbia, Missouri, and Colorado River systems. Aside from international political and environmental considerations, the proposal was sunk by a forecast return on investment of about 5 cents for every dollar invested. I wondered would the Mississippi water scheme have a better return?
Additionally, how would I register the feasibility of this scheme against the author’s contention that two reference projects — the California Aqueduct and the Alaska Pipeline — represented far more difficult projects than he envisioned this plan to be. Marshalling a few facts challenged that supposition.
The proposed flow of 250,000 gallons/second represents a lot of water. Converting it into a more normal engineering unit, this would represent about 32,000 cubic feet/second (CFS). That happens to be about the same rate of flow as passes through the generating turbines at Hoover Dam at full capacity. In the original letter, this flow was correctly calculated as the amount of flow necessary to fill Lake Power in one year. Even at today’s record low level, Lake Power is not empty. Lesser flows could reduce the costs and difficulty of the project while still providing significant benefits.
The Alaska Pipeline is a significant project. It involved construction, in forbidding conditions, of a 48-inch diameter pipeline about 800 miles long. The peak capacity flow rate is 2 million barrels per day, or about 100 CFS. So, as a comparison, pumping the proposed volume of water from the Mississippi would involve a distance approximately twice as long for a flow about 320 times as great.
The California Aqueduct involves a peak flow of 13,000 CFS over a distance of about 450 miles. As proposed, this Mississippi diversion project would involve 2½ times as much water over a distance nearly four times as long.
One big challenge of the California Aqueduct is pumping water to a height of 1,926 feet, which requires massive pumping equipment. Our Mississippi diversion scheme has a net difference in elevation of 3,700 feet from New Orleans to Lake Powell, or a terminus nearly twice as high as the highest point in the California Aqueduct. This last difference is especially significant because the fall from 1,926 feet to near sea level could, in theory, be used to generate some power to offset the pumping power requirement. That option is not fully available in pumping to 3,700 feet.
The peak elevations required for pumping the water are likely much greater than the net difference of 3,700 feet. If we discount the higher elevations the water has to be pumped to, we still have to provide the power to raise the water to 3,700 feet. Using the power plant at Hoover Dam as a reference, this would require about 12,000 megawatts of pumping power.
The power requirement of the flow would require at least the equivalent capacity of about 5½ times the power output of the new Plant Vogtle nuclear facility in Georgia. Plant Vogtle has been estimated to cost over $28 billion. Thus, our water pumping scheme could incur a cost of $150 billion for the power plants alone.
“Wait you say, what about wind power instead of nuclear? Surely that would be cheaper.” Yes, it would, but there are, of course, challenges. A wind turbine cannot reliably produce power 24 hours a day, 365 days a year. So the installed wind power capacity would be greater than the current capacity from the 150 wind farms in Texas.
As a nation, we have seemingly lost our appetite for large projects. I don’t think this one will overcome that reluctance.
John Homer is a professional engineer working in retirement as a consultant on construction projects. He lives near Indianapolis and can be reached at [email protected]
This article originally appeared on Palm Springs Desert Sun: Engineer evaluates idea of pumping water from Mississippi to West
Soruce : https://news.yahoo.com/engineer-heres-look-idea-pumping-120105563.html